Lieutenant Selden was the first man to mount.  But the Mexicans collected all their energies for this last moment.  A tremendous fire dashed the foremost of the stormers into the ditch, killing Lieutenants Rogers and Smith and clearing the ladders.  Fresh men instantly manned them, and, after a brief struggle, Captain Howard, of the voltigeurs, gained a foothold on the parapet.  M’Kenzie, of the forlorn hope, followed; and a crowd of voltigeurs and infantry, shouting and cheering, pressed after him, and swept down upon the garrison with the bayonet.  Almost at the same moment, Johnston, of the voltigeurs, who had led a small party round to the gate of the castle, broke it open and effected an entrance in spite of a fierce fire from the southern walls.  The two parties uniting, a deadly conflict ensued within the building.

Maddened by the recollection of the murder of their wounded comrades at Molino del Rey, the stormers at first showed no quarter.  On every side the Mexicans were stabbed or shot down without mercy.  Many flung themselves over the parapet and down the hillside and were dashed in pieces against the rocks.  More fought like fiends, expending their breath in a malediction, and expiring in the act of aiming a treacherous blow as they lay on the ground.  Streams of blood flowed through the doors of the college, and every room and passage was the theatre of some deadly struggle.  At length the officers succeeded in putting an end to the carnage; and the remaining Mexicans having surrendered, the Stars and Stripes were hoisted over the castle of Chapultepec by Major Seymour.

Meanwhile Quitman had stormed the batteries on the causeway to the east of the castle, after a desperate struggle in which Major Twiggs, who commanded the stormers, was shot dead at the head of his men.  The Mexicans fell back toward the city.  General Scott, coming up at this moment, ordered a simultaneous advance to be made on the city, along the two roads leading from Chapultepec to the gates of San Cosme and Belen, respectively.  Worth was to command that on San Cosme, Quitman that on Belen.  Both were prepared for defence by barricades, behind which the enemy were posted in great numbers.  Fortunately for the assailants an aqueduct, supported by arches of solid masonry, ran along the centre of each causeway.  By keeping under cover of these arches, and springing rapidly from one to another, Smith’s rifles and the South Carolina regiment were enabled to advance close to the first barricade on the Belen road, and pour in a destructive fire on the gunners.  A flank discharge from Duncan’s guns completed the work; the barricade was carried; and without a moment’s rest Quitman advanced in the same manner on the garita San Belen, which was held by General Torres with a strong garrison.